Proportional, integral and derivative (PID) controllers and other control loops are frequently used to monitor and control analog systems in mechanical control systems. PID controllers are generally designed to eliminate the need for continuous operator attention. For example, a home thermostat may be used to automatically hold the temperature at a set-point. In traditional PID loop control, various coefficients generally have to be configured and adapted to ensure efficient operation.
In general, the output of a PID controller may change in response to a change in a measured process variable of the system being controlled and the output of the PID controller may also change in response to a change in a setpoint or target value for the measured process variable. PID control loops frequently include three different modes. These modes are generally referred to as the proportional, the integral and the derivative. Each of these modes may have its own coefficient that must be configured properly for the PID control loop to function efficiently. Setting up and configuring the various coefficients of a PID control system may be referred to as “tuning” the PID control loop (or more generally, “PID tuning”). If not properly set up, changes in a setpoint or in the system load may result in excessive system oscillation or excessive error (e.g., between the setpoint and the measured process variable).
PID tuning frequently requires numerous monitoring and configuration steps performed by the technician or engineer tuning the system. For example, turning a traditional PID control system may involve: measuring the period of oscillation (e.g., the time of one complete control loop cycle), adjusting the proportional coefficient to obtain loop stability, calculating an interval coefficient to use, monitoring and evaluating the response of the control loop and adjusting the interval coefficient accordingly, determining any derivative coefficient needed, as well as testing the system by simulating sudden changes in system load to observe the response time to reach a new setpoint.
Additionally, PID loop algorithms may also require evaluating and adjusting initial constants and may include the added complexity of steady state error control as a supplemental algorithm in order to achieve control stability.